The present disclosure relates to an optical film and a method for manufacturing the same, an antiglare film, a polarizer with an optical layer, and a display apparatus. In particular, it relates to an optical film used in a display surface of a display apparatus such as a liquid crystal display apparatus.
In various display apparatuses such as liquid crystal displays, plasma displays, and cathode ray tube (CRT) displays, when external light such as a fluorescent lamp is reflected on the surface, a problem of a significant degradation of visibility occurs. Under these circumstances, recently, a method in which an optical multilayer film or a low-refractive-index film is provided on a surface of a display apparatus to decrease reflectivity and a method in which an optical film such as an antiglare film having fine irregularities on a surface thereof is provided to diffuse-reflect external light, thereby blurring a reflected image, have been employed.
However, the former method has the following problems. When such an optical multilayer film is used, the production cost increases and a sufficient antiglare property cannot be achieved. Even when the production cost is reduced by using a low-refractive-index film, reflection is not negligible because of a relatively high reflectivity. On the other hand, the method for blurring a reflected image by diffuse reflection using an antiglare film having fine irregularities on a surface thereof is widely used because of its low cost and high productivity.
FIG. 1 shows the structure of a conventional antiglare film. As shown in FIG. 1, an antiglare film 101 includes a base material 111 and an antiglare layer 112 provided on the base material 111. The antiglare layer 112 is constituted by a resin containing fine particles 113 composed of amorphous silica or resin beads. Fine irregularities are formed on the surface by protruding the fine particles 113 from the surface of the antiglare layer 112. This antiglare film 101 is formed by applying a coating material containing the fine particles 113, a resin, a solvent, and the like onto the base material 111 and curing the coating material. According to the antiglare film 101 having the above structure, since the fine irregularities on the surface of the antiglare layer 112 scatter light incident on the antiglare layer 112, reflection due to surface reflection is reduced.
However, the fine irregularities on the surface of the antiglare film 101 are constituted by the fine particles 113 protruding on the surface and a binder portion that connects between protrusions of the fine particles 113 with continuous slopes. Accordingly, although the antiglare film 101 has a high antiglare property, light that is transmitted through the antiglare layer 112 in the vertical direction is also strongly scattered, resulting in a problem of a decrease in the transmitted image clarity.
Consequently, as shown in FIG. 2, a conceivable approach to suppress the decrease in the transmitted image clarity is to decrease the filling ratio of the fine particles 113 in the antiglare layer 112 so as to increase the period of the irregularities on the surface of the antiglare layer 112. However, when the period of the irregularities on the surface of the antiglare layer 112 is increased to obtain gentle irregularities, a flat portion is formed at the binder portion between protrusions of the fine particles 113, resulting in a problem of a decrease in the antiglare property.
As described above, there is a trade-off between the antiglare property and the transmitted image clarity, and it is believed that it is difficult to achieve both these properties. However, recently, an antiglare film in which a decrease in the transmitted image clarity is suppressed while having an antiglare property has been desired. For example, technologies for reducing glaring and improving clarity by adjusting internal scattering while maintaining the antiglare property have been disclosed (for example, Japanese Patent Nos. 3,507,719 and 3,515,401).
However, as described above, since there is a trade-off between the transmitted image clarity and the antiglare property, it is difficult to improve the transmitted image clarity while maintaining the antiglare property. Although the antiglare property and the transmitted image clarity can be improved to some extent by the technologies disclosed in Patent Documents 1 and 2 mentioned-above, the degree of improvement is not sufficient, and further improvement in these two properties has been desired.
Also, in some cases, front surface plates for the purpose of providing mechanical, thermal, and weathering protections and a design function are arranged on the front surface (the viewer's side) of, for example, liquid crystal displays, organic EL displays, and other display apparatuses. In such cases, when a rear surface (display apparatus side) of a front surface plate has a flat shape and if, for example, the front surface plate is deflected and comes close to the display apparatus, a problem of occurrence of Newton rings occurs.
Furthermore, in the cases where another rear surface member is arranged at the rear surface side of a display apparatus, problems of deflection of members become severe, resulting in the problem of the occurrence of Newton rings. This is because the space between the display apparatus and the rear side member is narrowed with a reduction in the thickness of the display apparatus, and in addition, the size of the display apparatus is increasing. A description will be made using a liquid crystal display as an example. For example, in a liquid crystal display, a diffusing plate that makes the illuminance of light emitted from a light source uniform in a plane, a lens film for controlling the viewing angle, and a polarization separation reflective film that polarizes and separates light for reuse, and the like are arranged as the rear surface members. However, a polarizing plate disposed at the rear surface side of a liquid crystal panel and in front of these rear surface members usually has a flat surface profile. Thus, occurrence of Newton rings has been a problem in thin liquid crystal displays.
Consequently, an optical film that can suppress occurrence of such Newton rings has been desired.
Accordingly, it is desirable to provide an optical film and a method for manufacturing the same, an antiglare film, a polarizer with an optical layer, and a display apparatus that can achieve both good antiglare property and transmitted image clarity.
Furthermore, it is desirable to provide an optical film and a method for manufacturing the same, an antiglare film, a polarizer with an optical layer, and a display apparatus that can achieve both good antiglare property and image clarity and that can also suppress occurrence of Newton rings.